Horizontally elongated siding panels such as roll-formed sheet metal (e.g. aluminum) panels or molded plastic (e.g. vinyl) panels are widely employed for cladding exterior walls of buildings. Typically, the panels are mounted one above another on a wall in parallel, overlapping, interlocked relation with the surface of each panel sloping downwardly and outwardly so as to simulate the appearance of clapboards or other conventional wooden siding, and are attached to the wall at their top margins by suitable fastening means. Each panel has an outwardly projecting lip along its top margin, and an inwardly bent, upwardly opening channel flange at its bottom margin for overlying and interlocking with the lip of the next lower panel on the wall to secure the panel bottom edge (with the panel surface spaced from the surface of the lower panel) and to conceal the fastening means that hold the lower panel.
Siding panels of the type described above have conventionally been secured to walls by fasteners such as nails driven through a flat nailing flange provided at the panel top margin above the locking lip. See, for example, U.S. Pat. No. 3,150,464. This mounting arrangement is disadvantageous in that it is difficult to achieve proper positioning and alignment of the successive courses of panels, especially when installation is being performed by homeowners without experience or special equipment. The panels, being nailed to the wall, are not free to expand or contract with changes in temperature, and it is very difficult to remove them (for instance, to replace a damaged panel); moreover, the provision of a concealed nailing flange above the locking lip involves uneconomical consumption of the relatively expensive siding material.
As siding panels are usually applied to exterior walls of residences or other buildings, it is conventional to provide sheathing inwardly of the panels, and it is also commonly necessary to provide thermal insulation for the walls they cover. Some commercially available siding panels have layers of backers of insulating material adhered to their inner surfaces, both to strengthen them structurally and to provide the requisite insulation; but in general, with panels of this type there are discontinuities in the insulating layer, and consequent impairment of desired insulating effect, adjacent the junctures between panels.
Other wall-insulating arrangements are of course well known, but these are ordinarily unrelated to siding panels and require entirely separate installation with attendant inconvenient consumption of time and labor. Also, alternative panel-mounting arrangements have been proposed, using various types of clips or fastener strips for holding the panels, but these again generally require considerable care and skill in positioning and alignment, and in many cases do not permit ready removal of panels. Thus, they do not fully meet the needs of the "do-it-yourself" homeowner or other relatively unskilled worker.
U.S. Pat. No. 3,780,483 discloses a siding system constituted of insulation panels (backing boards) and interlocked outer siding panels, but does not provide for facilitating the achievement of a proper positioning and alignment of successive courses of siding panels.